1. Field of the Invention
The present embodiments relate to wafer processing apparatus, and more particularly, apparatus and methods for processing a wafer in a plasma etching chamber.
2. Description of the Related Art
The manufacturing of integrated circuits includes exposing substrates (e.g., wafers) to chemically-reactive plasmas to etch features. The features are then processed to define transistors, capacitors, vias, trenches, etc. The vias and trenches are used for placing the conducting interconnectors.
Non-uniform etching can adversely impact wafer yield. The non-uniform etching can be attributed to electromagnetic standing wave effect that has been observed in the plasma reactor caused by the radio frequency (RF) electromagnetic waves used during the etching process. The electromagnetic standing wave effect has been noticed to result in the formation of strong center-high etch rate pattern within a plasma reactor, particularly at very high frequency of 30 MHz and above. The standing wave effect and, hence, the center-high etch rate pattern is found, in at least some cases, to be significant when the reactor diameter is comparable to half of the effective RF wavelength provided in the plasma reactor. It would be beneficial to control the non-uniformity in the etching process by addressing the standing wave effect within the plasma reactor, particularly as the size of the critical dimension shrinks with each new generation of devices, and as wafer sizes increase, so as to facilitate production of higher number of devices from the same wafer. Thus, controlling non-uniformity is crucial to enabling more advanced technology nodes to be mass produced in a cost-effective manner.
It is in this context that embodiments of the invention arise.